In a conventional optical disc device, the information can be recorded by radiating a light beam on a disc-shaped recording medium for sequentially forming pits thereon. Typical of such optical disc devices is a CD-recordable (CD-R) conforming to the standard for a compact disc. The data structure of a CD-R may be further appreciated with reference to the application entitled "Apparatus and Method for Completing an Incomplete Recording on an Optical Disc", U.S. Pat. No. 5,559,778, assigned to the assignee of the present invention and incorporated by reference herein.
The optical disc employed in the CD-R drive device is a write-once optical disc in which a light beam of high intensity is radiated thereon for altering optical properties of the recording layer between pre-grooves, which are pre-formed guide grooves, for writing the information only once.
On the write-once optical disc, there is provided a program area for recording data per se, such as speech data. Several methods of data recording may be used which fall under one of two categories; uninterrupted writing (or disc at once (DAO)) and uninterrupted writing. The latter category includes track at once (TAO) and packet recording (fixed or variable packet). The present invention relates to uninterrupted writing.
One method for data recording in the program area is a track-based write-once operation of subsequently writing data track-by-track. In the present specification, "track" means a collection of data corresponding to a file or two or more files.
On the write-once optical disc, a lead-in area is formed inwardly of the program area, that is towards the disc center. The lead-in area is a region in which there is recorded management data for management of data recorded in the program area. Adjacent to the lead-in area towards the center of the disc is a program memory area (PMA). The PMA functions as a temporary memory for storing disc identification information as well as data indicating the portions of the disc that have been used for recording. Additionally, the PMA stores information concerning the start address and the end address of a track. The start and end address of the data recorded in the PMA area help define a unrecorded area in the PMA so that data may be written to this unrecorded area.
However, there are also occasions wherein data is written once on the basis of a packet recording, a packet being a unit of data smaller in size than a track. The packet-based data write-once operation is termed the "in-track write-once" operation. In this case, each track is made up of a variable number of packets and the information concerning the track start and end addresses are previously recorded in the PMA area. In the "in-track write-once" operation, data is sequentially recorded in succession, beginning from the first packet in the track. After interruption of the data recording operation, data recording is re-started at the unrecorded area next to the area in which the last data has been recorded.
An important difference between the two aforementioned methods is that information concerning identification of those portions of the PMA having data recorded thereon (i.e., the "use state") is recorded in the PMA only on the track basis. The information concerning the "use state" of the program area on the packet basis is not recorded in the PMA Consequently, for the "in-track once-write" operation, recorded data is directly read out for detecting the unrecorded area, that is for determining whether a subject area is a pre-recorded area or an unrecorded area. To this end, a binary search method is generally employed. However, with the binary search method, the search time becomes longer as the number of physical tracks making up a track becomes larger. As used herein, the "physical track" means an area scanned by an optical pickup during one complete revolution of the optical disc during data readout.